Field:
This disclosure is concerned generally with a method of determining a serum antibody titer and specifically with using PRN techniques to determine influenza antibody titers in serum samples.
Prior Art:
It is well known that the titer of a given antibody in a blood serum can be determined by taking advantage of the antibody's complexing properties and/or high specificity for its corresponding antigenic substance. Typical techniques for determining serum antibody titers include immunoassays, hemagglutination inhibition (HAI), and plaque reduction neutralization (PRN) methods. PRN techniques are described more fully in, for example, B. D. Davis et al., The Nature of Viruses in Microbiology, pp. 1044-1045, Harper & Row, New York, 1968.
Titration of serum influenza antibody levels is commonly done via HAI technique as introduced by Hirst, G. K., J. Exp. Med. 75:47-64, 1942. The antibody measured is directed to hemagglutinin, a viral surface antigen. A prerequisite for measuring the antibody content of serum involves treatment of the serum with materials such as kaolin or receptor destroying enzyme (RDE) to remove nonspecific inhibitors. The most commonly accepted method of treatment is that of using RDE (see, for example, Measurement of Hemagglutination-Inhibition Antibody to Influenza Virus in the 1976 Influenza Vaccine Program: Methods and Test Reproducibility, Gary R. Nobel, et al., from the World Health Organization Collaborating Center for Influenza Virology Division, and Statistical Activities, Bureau of Laboratories, Center for Disease Control, Atlanta, Georgia in the Journal of Infectious Disease, Vol. 136 Supplement, pp. 5429-5434, December 1977).
Although PRN techniques have been used to determine antibody titers to some other viruses, we are unaware of any prior use of our methodology for the determination or titration of serum influenza antibody levels. We have now found that it is possible to accurately determine serum influenza antibody titers using a PRN technique. Quite surprisingly, the technique results in greater sensitivity and specificity than existing HAI methods and is more useful than HAI methods in determining anti-infective influenza antibodies.